Extruding apparatus is known in which two extruders are arranged in an L-shape configuration so that one extruder is fed by the other. Each of the extruders comprises a casing having a cylindrical bore and having inlet and discharge openings. A screw is rotatable in the cylindrical bore of the casing by drive means located at the end of the casing opposite the discharge. The discharge of one extruder is connected to the inlet of the other so that material extruded by the first extruder is fed into the second extruder.
In order to effect a degassing of the material, a vacuum is applied to the interior of the second extruder in the vicinity of the inlet opening so as to draw off gas inclusions from the material fed into the second extruder from the first extruder. However, it has been found that thorough and effective degassing of the material is not obtained so that gas inclusions still remain in the material as it is propelled by the extrusion screw toward the discharge of the second extruder.